1. Field of the Invention
This invention relates to an electrophotographic apparatus, or more in particular to an electrophotographic apparatus capable of selectively producing either an ordinary electrophotographic copy or a copy master developed by a toner containing a sublimable dye and thermally transferable to another recording medium.
2. Description of the Prior Art
An image depicted on such a primary recording medium as paper or cloth by means of a sublimable dye may be thermally transferred to a desired secondary recording medium such as paper or cloth. This thermal transfer is easily accomplished by ironing the primary recording medium, namely, copy master carrying an original image, which is superposed on the secondary recording medium. Several operations of heat transfer are possible on one sheet of copy master. In this type of copying, the image formed on the secondary recording medium must be an erect image, requiring an inverted image to be formed on the copy master. In the prior art, such a copy master is produced by offset printing. The production of the copy master by offset printing process, though convenient for mass production of masters involving a single image, is not an economical means for producing copy masters of a variety of different images, each in a small number. Further, this offset printing process is not a suitable method for quickly producing copy masters of images tailored to individual requirements. To overcome this problem, a process for producing a copy master by electrophotography has been suggested. This electrophotographic process of copy master production is possible by the same operation as an ordinary copying machine and therefore provides a convenient means for copying a great variety of images desired by individuals. This copying machine for producing copy masters, if constructed to include an optical system for forming an inverted copy image and use a developing toner containing a sublimable dye, may be fabricated in the same manner as an ordinary electrophotographic apparatus. Application of the electrophotographic apparatus as a single-purpose machine only to the production of copy masters reduces the utilization factor of the machine, resulting in a higher unit cost of copy masters.